Possibly incorrect date of birth of Yvonne Constant

Yvonne Constant's page says that Yvonne Constant was born on June 15, 1930. This contradicts the article in Le Télégramme (in French), which says that her birthday was at the end of the year. It appears that before the announce of her death, many websites, including the IMDb, were giving June 15, 1935. Some of them just changed the year from 1935 to 1930 to match the announced age of death (92 instead of 87). Did the IMDb check the date of birth (e.g. on the birth or death certificate), or was the year of birth just changed without any verification?